In recent years, a portable wireless terminal such as a cellular phone, a wireless LAN terminal, etc., is rapidly becoming widespread. In particular, as cellular phone become smaller and lighter due to technological advances, it is common to carry a cellular phone all of the time in daily life. In addition to a conventional voice call function, the cellular phone is gaining greater functionality such as a personal information terminal that stores and manages data of various kinds, such as individual-based confidential information, etc.
As a result, users who have lost their cellular phones through carelessness, theft or for other reasons suffer from problems in that tolls are often improperly charged to authorized terminal owners or confidential data (for example, a phonebook, an email address book, schedule information, an electronic purse, etc.) is used improperly. Therefore, there is a need for a means in order to prevents improper use of lost or stolen cellular phones.
As one security function for cellular phones, a dial-lock function by means of a personal identification number is conventionally used to prevent a calling operation by a third party who does not know the personal identification number. The owner of the lost or stolen terminal usually informs a central exchange office, etc., of the loss or theft so that the central exchange office can stop calls to/from the terminal.
Further, there is disclosed a technique in which the owner of the lost or stolen terminal makes a call to the terminal in question from an ordinary telephone so that stored data in the terminal is deleted in order to prevent reading of the stored data by remote control. (See Patent Document 1.) Still further, there is disclosed a technique in which stored data of the lost or stolen terminal is uploaded to a service center by remote control, backed up, and after the terminal has been found, saved data is downloaded from the service center in order to restore the terminal to its original state. (See Patent Document 2.)
[Patent Document 1]    Japanese Unexamined Patent Publication H07-193865
[Patent Document 2]    Japanese Unexamined Patent Publication 2000-270376